A Precise Timing Solution for IEC 61850-Compliant Digital Secondary Substation Applications

Precise time is crucial for power system applications. Line current differential relays using the SV protocol traditionally depend on discrete GNSS clocks at each substation. Process interface units sample ac quantities and generate SV frames with time stamps. In IEC 61850-based 87L protection, relay and PMU applications leveraging SV with locally and remotely acquired ac quantities require a global time reference.
Utilities have grown dependent on GNSS reliability at each substation. If GNSS traceability is lost, the algorithms relying upon it may become unavailable or misoperate. Redundant GNSS clocks are still susceptible to interference, spoofing, and jamming. Modern timing technologies can mitigate disruptions to the GNSS.

The authors designed and tested a system to mitigate issues from GNSS outages. The team validated a solution using ePRTCs and TDGs. The TDG network references IEEE 1588 PTP G.8275.1 from the ePRTCs through a timing aware telecom network. The solution maintains time accuracy after losing GNSS and demonstrates the survivability of substation functions dependent upon time synchronization used for the SV protocol. Protective relay data demonstrate that this solution provides utility-wide synchronization in the loss of GNSS for classic utility relaying and IEC 61850-compliant DSSs.